(1) Field of the Invention
This invention relates generally to a system for preventing damage to a propeller, and more particularly to an apparatus for preventing a propeller of a countermeasure device from deflecting to the point of being damaged.
(2) Description of the Prior Art
Underwater vehicles, such as torpedoes and countermeasures, such as torpedoes, utilize a propeller system to provide hovering and transit capabilities. An example of such a propeller system is shown in FIG. 1, which is a partial cross-section view of a countermeasure device 100. Countermeasure device 100 includes a nose portion 102 and a tail portion 104. Tail portion 104 includes a tail cone 106, a shroud 108 and a two-bladed propeller 110 mounted on a shaft 112, which is driven by a motor located within tail cone 106. FIG. 1 shows a cross-section view of shroud 108 only, all other features are shown in full. FIG. 1A shows an end view of countermeasure device 100, including tail cone 106, shroud 108 and two-bladed propeller 110. Shroud 108 includes shroud supports 113 and shroud ring 114. Countermeasure device 100 is mounted inside a launch tube 116 of a vessel 118, as shown in FIG. 2. When countermeasure device 100 is launched, it pushes end cap 120 of launch tube 116 open. Upon the opening of end cap 120, water 122 rushes into launch tube 116 at a pressure which varies depending on the depth in water 122 that the launch tube 116 is located. The difference in pressure between launch tube 116 and water 122 creates a water hammer which can impact propeller 110 and shaft 112 with great force. The force with which the water hammer impacts propeller 110 and shaft 112, both when entering launch tube 116 and after impacting rear wall 124 of launch tube 116 and then exiting launch tube 116, can be great enough to cause propeller 110 and, consequently, shaft 112 to deflect, permanently damaging propeller 110 and shaft 112, thereby rendering the countermeasure device 100 less maneuverable or inoperable.